Effects of drugs on mucus clearance

Mucociliary clearance (MCC), the process in which airway mucus together wit h substances trapped within are moved out of the lungs, is an important def ence mechanism of the human body. Drugs may alter this process, such that i t is necessary to know the effect of the drugs on MCC. Indeed, agents stimu lating MCC may be used therapeutically in respiratory medicine, especially in patients suspected of having an impairment of their mucociliary transpor t system. In contrast, caution should be taken with drugs depressing MCC as an undesired side-effect independently of their therapeutic indication. Si nce cough clearance (CC) serves as a back-up system when MCC fails, the inf luence of drugs must be examined not only on MCC but also on CC. Ultimately the clinical repercussions of alterations in mucus transport induced by dr ug administration must be studied. Tertiary ammonium compounds (anticholinergics), aspirin, anaesthetic agents and benzodiazepines have been shown to be capable of depressing the mucoci liary transport system. Cholinergics, methylxanthines, sodium cramoglycate, hypertonic saline, saline as well as water aerosol have been shown to incr ease MCC. Adrenergic antagonists, guaifenesin, S-carboxymethyl cysteine, so dium 2-mercapto-ethane sulphonate and frusemide have been reported not to a lter the mucociliary transport significantly. Amiloride, uridine 5'-triphos phate (UTP), quaternary ammonium compounds (anticholinergics), adrenergic a gonists, corticosteroids, recombinant human deoxyribonuclease (rhDNase), N- acetylcysteine, bromhexine and ambroxol have been reported either not to ch ange or to augment MCC. Indirect data suggest that surfactant as well, as a ntibiotics may improve the mucociliary transport system. As for the influence of drugs on CC, amiloride and rhDNase have been demons trated to increase the effectiveness of cough. A trend towards an improved CC was noted after treatment with adrenergic agonists. The anticholinergic agent ipratropium bromide, which is a quaternary ammonium compound, has bee n suggested to decrease CC significantly. Bromhexine, ambroxol and neutral saline seemed not to alter CC, either positively or negatively. Finally, treatment with either amiloride, recombinant human deoxyribonuclea se, bromhexine, ambroxol, N-acetylcysteine, S-carboxymethylcysteine or hype rtonic saline has been suggested as a possible cause of clinical improvemen t in patients, such as the experience of dyspnoea, the case of expectoratio n or the frequency of infective exacerbations. Other agents did not show a clinical benefit.